KEVOS® MAKEOS · Engineering
Preferred Size Selection (Renard Series Size for Each Requirement, Oversize, Distinct Sizes)
For a set of required sizes or ratings, which preferred numbers should I pick, how much oversize does each choice give, and how many distinct sizes does the range need?
Selection of preferred sizes from a Renard series (R5 to R80) for up to five requirements: the ratio of the series and the preferred numbers around each requirement (as the preferred numbers tool), the smallest preferred number at or above each requirement and its rounded value, the oversize of each choice, and the number of distinct sizes, against the largest oversize you accept.
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How this tool works
Inputs, units and where to find them
| Input | Unit | Typical source |
|---|---|---|
| Series | choice | Renard series to choose from (finer series give smaller steps). |
| Requirement 1 (0 = unused) | First required size or rating. | |
| Requirement 2 (0 = unused) | Second requirement. | |
| Requirement 3 (0 = unused) | Third requirement. | |
| Requirement 4 (0 = unused) | Fourth requirement. | |
| Requirement 5 (0 = unused) | Fifth requirement. | |
| Largest oversize accepted | % | Largest amount a chosen size may exceed its requirement. |
Method and formulas
- Series ratio = 10^(1/n); preferred numbers 10^(i/n) (as the preferred numbers tool).
- Chosen size = 10^(⌈n log₁₀ r⌉ ÷ n), the smallest preferred number at or above the requirement; rounded to three figures as usually listed.
- Oversize = chosen ÷ required − 1.
- Example: the largest oversize is 11.111% with 5 distinct sizes.
Limitations
- Exact series values; the rounded values used in standards differ slightly (for example 3.15 for 3.162).
- Each requirement taken as a minimum; round down instead when the requirement is a maximum.
- Example values are illustrations. Replace them with values for your actual task.
Typical uses
- Choose tank, motor or pulley sizes from a preferred series
- Rationalise a product range
- See how a coarser series changes the oversize
Who it is for
- Design engineers
- Product managers
- Standards engineers
What you get
- Preferred size for each requirement
- Oversize of each
- Distinct sizes and decision
Interpreting the result
- The worst oversize of a series is its step: about 58% for R5, 26% for R10, 12% for R20.
References
- Machinery’s Handbook, 29th edition (Industrial Press, 2012), printed pp. 672. Topic reference; no source tables or recommended settings are reproduced.
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